September 1978

The Journal ofP E D IA TRICS 435

Standard growth curves for achondroplasia

Standard growth curves Jor achondroplasia. the most common form of short-limbed dwarfism. have been
constructed based on measurements oj height. growth velocity, upper and lower segment, and head
circumference in 400 achondroplastic dwarfs. These standard curves provide the basis to assess normal
growth in these individuals, to aid in the determination oj superimposed disorders, and to assess any
growth accelerating therapy.

William A. Horton, Jerome I. Rotter, David L. Rimoin,* Torrance, Calif.,

Charles I. Scott, Houston, Texas, and Judith G. Hall, Seattle, Wash.

ACHONDROPLASIA is the most common form of short- METHODS

limbed dwarfism. Although the clinical and radiologic Measurements of total height, upper and lower
features have been well characterized, surprisingly little segment, and head circumference were obtained on 403
attention has been given to the study of growth patterns in patients with achondroplasia ascertained through short
this disorder.' Nehme et al' have recently published stature clinics at UCLA-Harbor General Hospital,
height and skeletal growth curves for achondroplasia, but Torrance, Calif., the University of Washington School of
their data were based on only 18 patients; thus they were Medicine, Seattle, Wash., the University of Texas Medical
able to report only average values, without any measure School at Houston, and the 1976 National Convention of
of variance. Because of the need for this type of informa- the Little People of America. The sample included 189
tion in the management of individual patients and in the males and 214 females. Patients treated with potential
evaluation of potential growth acceleration therapy, we growth acceleration drugs, such as fluoxymesterone, were
have measured height, growth velocity. upper and lower excluded from the study for the period during and after
segment, and head circumference in over 400 classical such treatment. Head circumference measurements from
achondroplastic dwarfs. Using these data, standard patients known to have had previous shunt procedures for
growth curves have been constructed. (Preliminary curves hydrocephalus were also excluded.
based on measurements on 140 individuals were Achondroplasia is a specific chondrodystrophic disor-
presented at the 1976 Birth Defects Conference, Vancou- der with characteristic and specific clinical and radio-
ver, Canada.") graphic features.' Only those individuals satisfying the
strict diagnostic criteria for achondroplasia were included
in this study by the three participating bone dysplasia
From the Division of Medical Genetics, centers. Measurements were made as part of ongoing
UCLA-Harbor General Hospital, the Department of evaluation in the Short Stature Clinics and by one of us
Pediatrics, University of Texas Medical School,
Houston, and the Department of Pediatrics, University (W. A. H.) at the Little People of America National
of Washington School of Medicine. meeting. Most of the measurements were casual and
Supported in part by United States Public Health retrospective, but were done in clinics specializing in the
Service Grants HD 05624, HD 11966, HD 00417, evaluation of short stature, which expend a great deal of
AM-050602. RRO 0425, a Research and Birth effort in standardizing their measurement techniques.
Dejects Center Grant from the National Graphic methods were used to construct preliminary
Foundation-March of Dimes, and the Easter Seal
Research Foundation.
growth distance curves for height, upper and lower
"Reprint address: Divtsion of Medical Genetics, Harbor segment, head circumference, and growth velocity curves
General Hospital, 1000 West Carson St., Torrance. CA 90509. for height.' A combination of cross-sectional and longitu-

0022-3476178/0393-0435$00.4010 e 1978 The C. V. Mosby Co. Vol. 93, No.3. pp. 435·438
436 Horton et (/1. 'I'l", JOIII'I/(/I ol Pedicill'lcs
Seplemb('" 1978

leo - ACHONDROPLASIA - 160

HEIGHT L
Mol-e N"169

140

14 0
120+--+-+--+

E 120 E
(J 100
o -I--j--I--I-,JL-¥ '+-:;+"::
1oo-l- - f- l--.-t'-.AF-

eo

NORMAl.
___ , ~ _.__..- -- ,,,~' .-_-,""-,"-_... ...
_~ ;;O "2~~~ Ij ' 1i ~ ~~m...
~~
60 ~~_ '7 %
_ _ NIAll
- - - ~'Il,
~ ~CIA:,l :"..":' ~~AH
1---J..-l---I--I-t-I-!:--+~:l-l-l-I-+-1---l--1--l
4 B 1234567 B9 10111213 141516 17 18

AGE - Yeers AGE -Years

Fig. I. Height (mean ± SD) for mules with nchondroplasla Fig. 2. Height (rneun :l: SD) for Icmulcs with achondropluslu
(stippled urea) co mpared to normal male stan dard height curve (stippled urea) compared to normul Iumulc sumdurd height
(third , fiftieth, find ninety-seventh percentile). curve.

dinal data was used for the distance curves, and longitu- out the first decade. (This is distinctly abnormal when (me
dinal data for velocity curves. For all cu rves, the mean ± 2 cons iders that in normal individuals the growth rate varies
SD was plotted for achondroplasia and compared to cons istently above lind below the mean during this period
standard curves showing the normal third, fiftieth, and of time, rather than following a certain velocity percentile
ninety-seventh percentiles for heigh t and height velocity, as is usual for distance percentiles. For example, II normal
and mean ± 2 SD for upper an d lower segments and for indi vidu al growing consistently lit the third velocity
head circumference. The normal height and height veloc- percentile would rea ch a final heigh t of less than four feet
ity curves were taken for Tanner and Wh itehouse." The (120 em] compared to an individu al following the ninety-
estimates of normal upper and lower segment lengths seventh velocity percentile whose adult height woul d be
were calculated from the upper/lower segment ratio near seven feet [210 em].) Unfortunately, beyond age 10
standards derived by Mck.usick," and the normal height years, the number of measuremen ts is small and we
curves of Tanner and Whitehouse." The 'curves of Nell- cannot be certain if there is a pubertal growth spurt,
haus' were used for head circumference standards. In the although the few longitudinal observations suggest that
velocity curves, when mean velocity and standard dev ia- such a spurt occurs . In addition , the increased vari ability
tions for achondroplasia could not be plotted because of in velocity that is normally seen during adolescence was
insufficient longitudinal data, sin gle velocity measu re- also seen in the achondro plastic subjects, sugges ting that
men ts were plotted a nd connected by a dotted line , som e individuals were undergoing a growth spurt while
others were not during each measurement period . Fu rther
RESULTS· observations during this age period will be requ ired to
As seen in Figs . I and 2, the male and female height clarify this maller. Otherwise, the shape of the height
distance curves are very similar. The range of birth length velocity curves appears entirely normal for both males
for achondroplasia overlaps the lower range of normal, and females with achondroplasia.
whereas height progressively falls below norma! with Upper and lower segment lengths in achondroplasia are
time. The mean ad ult heigh t (ta ken at 18 years) is 7 ern plotted in Figs. 5 and 6. As expected, s ince acho nd rop lasia
greater for males than for females with achondroplasia. is a form of short-limbed dwarfism, their upper segment
Mean grow th velocity appears to be normal during the lengths are normal and the lower segm ent lengths milch
first year in ach ondrop lasi a (Figs. 3 and 4). Beyond below the norm al range for both male s and fema les. In
infancy, however, the growth rate drops to approximately contrast to our earlier observations based on 140 individ-
the third percentile for normal, where it rema ins through- uals, in whom the lower segment length was apparently
similar in the two sexes, but the upper segment length
'Copies of these charts may by obtained by writing Dr. Da vid Rirnoin, greater for males, " both upper and lower segments are
Harbor General Hospital, 1000 West Carson St., Torrance, CA 90509. slightly greater in the male in this expanded sample.
Volume 93 Standard growth curves for achondroplasia 437
Number 3

,.--~ -

25 ACHONDROPLASIA
GROWTH VELOCITY; ACHONOROPt..ASIA NORMAL

+
+ZStl
HEIGHT !olEAN
- - - '11'%
--IlIUN I-- f---
I Mal. N,26 --- 311.
I
20 I
'"
r...
o 1\ \
~ 15
<, \ ,
E \ ,
o 10
\

r-,
'-,
- -, - -, ~

,
-- -
,I
'\ ,/
"
h"-J , T -,--- - t -~ r1• " ....
-,,
260

t~
T
\

-+- - ...... - - ~, ~, ...

5
:! t i T "T -t-
.'
, 160
-~- E••

- ~~
" v., I SO
Z60
8 2 3 4 5 6 7 8 9 10 II 12 13 14 15 16 17 18
AGE - Years
'FIg. 3. Height velocity (Olean [heavy line] ±2 SO) for males with achondroplasia compared to the normal male
standard growth velocity curve.

25 I--- ACHONDROPLASIA
ACHONDROPI..,,O,SIA
GROWTH VELOCITY: NORMAL
~I
+
+250
HEIGHT IoIEAN
---
- - MEAN
97%
l-
\ Female N"'~5 -280
--- 3'1lo
20
l0-
a \
\
Q) 15
~
,sr"-"
\
\

E ,,\
o 10 ...
-- :-,.--- -- -~
- -, ...

5
t
1

~ T I I
+
~
.,..
I
.-- f-"
~: . - ,I'!l.'
-,
' .... ,
->,

r- ,,'
I-

,
roo +I 5D

""EI.tt
- I 50
o
2 3 4 5 6 7 8 9 10 II 12 13 14 15 16
AGE - Years
Fig. 4. Height velocity (mean [heavy line] ± 2 SO) for females with achondroplasia compared to normal female
standard velocity curve.

At birth, the mean head circumference for achondro- percentile and then leveling off; and a third, depicted by
plasia is slightly more than 2 SD above the normal (Figs. 7 Figs. 7 and 8, with gradually increasing head size during
and 8). During the first year, when rapid head growth the first year. More individual longitudinal data will be
occurs, this mean rises further above the normal range, needed to confirm or refute this impression.
after which a relatively constant relationship is main-
DISCUSSION
tained between achondroplastic and normal head circum-
ference into adulthood. There is, however, considerable Standard growth curves for height, height velocity,
overlap between the head circumference in achondropla- upper and lower segments, and head circumference have
sia and in the normal population. As in normal individu- been derived from measurements of over 400 individuals
als, head circumference is slightly greater at all ages for with classic achondroplastic dwarfism. These curves
males compared to females with achondroplasia. It is the should prove useful in following the individual patient
clinical impression of one of us (1. H.) that there are three with achondroplasia. The plotting of an affected child
dilTerent head circumference growth curves in achondro- within the "normal range" for achondroplasia may
plasia: one in which the head is large at birth and grows comfort the anxious patient or his parents. Growth
parallel to but above the ninety-seventh percentile; a measurements differing notably from those expected from
second in which the head is normal, or slightly large at the curves might indicate that some factor in addition to
birth, but grows dramatically, crossing the ninety-seventh achondroplasia is interfering with growth, or alternative-
 438 Horton et al. The Journal of Pediatrics
September 1978

100 ACHONDROPLASIA .+__.j_ -I-+_+_+-+-

UPPER/LOWER
SE~MENT -l--I--+- I- f-
Mo" N ,;7fi
60

E 90
u
70
60

40
~~-++-I-~.j--l--+-",,+"'-e-l"::C-+-=:l==~=
E 50
U

40
,, ~...
--- ,. - .:;..:.- .::_~;-,;n
:::~---~i~~~
._ -
---_.-
-
r"':":~-+--+--I--- - -- - - --
At H OhOROP L4~ 1 '" NORM AL.

3o-l--I- +--+- +--+-t---t--I- is :1'.:° ::-:-:- ;~~

~ _.'0
3 6 12 16 16 21 4 6 10 14 16
MONTHS YEARS
30 AGE
Fig. 7. Head circumference (mean ± 2 SO) for males with
2 3 4 5 6 7 B 9 10 II 12 achondroplasia (stippled area) compared to normal male head
AGE -Years circumference (mean ± 2 SO),

Fig. 5. Upper and lower segment Lengths (mean ± 2 SD) for

males with achondroplasia (stippled area) coin pared to normal
upper and lower segments (mean ± 2 SD).

60

tOO

E 50
BO'+-+-- I----I-+- -1-+-+-+-I-- +._~
U

60I-l--I--+: 40-

E 90 40 ~OA~A,1.

u 1--1-++-1--+-1---'1-1=1
::.:. ~::~ ......-.-.-
.. ....... atll

70
E 9 12 16 16 21 2
MONTHS YEARS
AGE
5
Fig. 8. Head circumference (mean ± 2 SD) for females with
achondroplasia (stippled area) compared to normal female head
circumference (mean ± SD).

12 13 14 15 16 17 IB
REFERENCES
AGE - Years
I. Rimoin DL : The chondrodystrophies, Adv Hum Genet S:I,
Fig. 6. Upper and lower segment lengths (mean ± 2 SD) for
1975.
females with achondroplasia (stippled area) compared to normal
2. Nehme AE, Riseborough EJ, and Tredwell SJ: Skeletal
upper and lower segments (mean ± 2 SD).
growth and development of the achondroplastic dwarf, Clin
Orthop 116:8, 1976.
ly, that the patient does not have achondroplasia. Further- 3. Horton WA, Rotter JI , Kaitila i, Gursky J, Hall JG, Shepard
more, such standard curves for achondroplasia must be TH , and Rimoin DL: Growth curves in ach ondroplasia,
used to assess properly any potential growth accelerating Natural History of Birth Defects: Original Article Series,
treatment. 13(3C):IOI,1977.
4. Tanner J\1 , Whitehouse RH , and Tukaishi M : Standards
Hydrocephalus is frequently suspected in the achondro-
from birth to maturity for height, weight, height velocity.
plastic infant due to his unusual head shape, relatively and weight velocity: British Children, 1965, parts I and II,
large head circumference and delayed motor develop- Arch Dis Child 4]:454 and 613, 1966.
ment. Plotting the child's head circumference on these 5. Tanner JM, and Whitehouse RH: Growth and development
head circumference curves may demonstrate the normal- records, Bull Plain, Herford, England, 1975, Creaseys Ltd.
6. McKusi ck VA: Her itable disorders of connective tissue, St.
ity of his head size for his basic disease and thus prevent
Lou is, 1972, The CV Mosby Company, p 73-74.
unnecessary diagnostic or even therapeutic measu res. 7. Nellhaus G: Composite intern ational and iterracial graphs,
Similar growth curves would be useful for each of the Pediatrics 41:106 , 1968.
skeletal dysplas ias.